Overrunning roller clutches are used in many automotive applications, especially in automatic transmissions, to provide selective relative rotation between a pair of races. A clutch cage, which is often integrally molded of plastic, is adapted to be installed in an annular space between the races. The races are maintained in a coaxial relation by bearing portions of the clutch cage, generally called journal blocks. The journal blocks must be as radially wide as possible in order to fit as closely as possible between the races, and thereby maintain the races as rigorously coaxial as possible. The annular space between the races also represents an upper limit on the potential radial width of any other clutch component that is located between the races when the clutch is installed.
One such component is the roller energizing spring, one of which is provided for each roller. The typical energizing spring, known as an accordion spring, is stamped from flat spring steel stock with a series of flat leaves joined in a V shape at a fold or pleat. The front end leaf engages the roller, while the back end leaf is joined to some part of the cage. Thus, the end leaves do not represent active parts of the springs. The pleats are the active part of the spring, the part that stores spring energy and determines how much work the spring can do on its roller. Accordion springs may be stamped with pleats that are axially or radially disposed, as a matter of design choice. Axial pleat springs are easy to install, in that the front leaf may be easily shaped to conform to the roller, while the rearmost pair of leaves may be easily shaped to press fit over some part of the cage as the spring is pressed radially into the cage. A drawback of axial pleat springs is that their leaves, which are radially disposed, block the annular space between the races. If a lubricant is radially directed through the annular space, as it often is, its flow may be disturbed, or may disturb the spring.
Thus, radial pleat springs may be preferred in such environments, since their leaves are axially disposed, and thus do not appreciably block oil flow. With a radial pleat spring, however, the annular space represents an upper limit on the radial width of the pleat, and thus a limit on the strength of the spring. Also, the endmost pair of leaves of a radial pleat spring opens axially, not radially, and so cannot be made to grip some part of the cage during spring assembly. As a consequence, the typical way of retaining a radial pleat accordion spring is to capture the entire radial width of the end of the spring in a slot in the end of the cage journal block. If the radial width of the spring is maximized, then the slot must be as wide, weakening the end of the journal block. In such a case, the journal block may have to be lengthened, or otherwise strengthened, to compensate. If the radial width of the spring were lessened, so as to fit in a narrower slot, then the size and strength of the spring pleat would be reduced. In that case, a heavier and more expensive metal stock may have to chosen for the spring. A new means of spring retention that did not require such a compromise between journal block and spring strength would be desirable.